Summary
Http4s Ember HTTP/2: unbounded inbound body buffering
Ember's HTTP/2 stack replenishes the inbound flow-control window based on bytes
received off the wire, not bytes consumed by the application. Received DATA is buffered in an unbounded per-stream channel. Flow control therefore
provides no backpressure: a peer can stream a large or unbounded body faster than the application drains it and the connection retains every payload in heap.
This is the read-path mirror of the outbound queue issue.
This affects an Ember receiving a request body and an Ember client receiving a response body from a hostile server.
Workarounds
- Disable HTTP/2 to remove the vector entirely.
- Apply an aggregate request-entity size limit (e.g.
EntityLimitermiddleware) on routes that consume the body. - Ensure handlers fully drain request bodies with aggressive idle timeouts.
Impact
Unauthenticated remote denial of service (OOM) against any Ember server built.withHttp2 for a non-draining or slow-draining route, and against an Ember client consuming from a hostile or compromised server.
Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service. Typical impact: denial of service.
CVE-2026-69202 has a CVSS score of 7.5 (High). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (0.23.35, 1.0.0-M47); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
Already deployed Kodem?
See it in your environmentNew to Kodem? Get a demo →Remediation advice
org.http4s:http4s-ember-core_2.12 to 0.23.35 or later; org.http4s:http4s-ember-core_2.13 to 0.23.35 or later; org.http4s:http4s-ember-core_3 to 0.23.35 or later; org.http4s:http4s-ember-core_2.13 to 1.0.0-M47 or later; org.http4s:http4s-ember-core_3 to 1.0.0-M47 or later
Kodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.
Frequently Asked Questions
- What is CVE-2026-69202? CVE-2026-69202 is a high-severity uncontrolled resource consumption vulnerability in org.http4s:http4s-ember-core_2.12 (maven), affecting versions <= 0.23.34. It is fixed in 0.23.35, 1.0.0-M47. Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service.
- How severe is CVE-2026-69202? CVE-2026-69202 has a CVSS score of 7.5 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which packages are affected by CVE-2026-69202?
org.http4s:http4s-ember-core_2.12(maven) (versions <= 0.23.34)org.http4s:http4s-ember-core_2.13(maven) (versions <= 0.23.34)org.http4s:http4s-ember-core_3(maven) (versions <= 0.23.34)
- Is there a fix for CVE-2026-69202? Yes. CVE-2026-69202 is fixed in 0.23.35, 1.0.0-M47. Upgrade to this version or later.
- Is CVE-2026-69202 exploitable, and should I be worried? Whether CVE-2026-69202 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-69202 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-69202?
- Upgrade
org.http4s:http4s-ember-core_2.12to 0.23.35 or later - Upgrade
org.http4s:http4s-ember-core_2.13to 0.23.35 or later - Upgrade
org.http4s:http4s-ember-core_3to 0.23.35 or later - Upgrade
org.http4s:http4s-ember-core_2.13to 1.0.0-M47 or later - Upgrade
org.http4s:http4s-ember-core_3to 1.0.0-M47 or later
- Upgrade